Anhydride functionalized cyclic polyorganosiloxane

Abstract

The present invention is a compound of Formula 1: where each R is a C3-C12-alkyl anhydride group; the sum of m and n is in the range of from 1 to 4; and -DHx- is a diradical of the compound of Formula 2: where x is from 3 to 10; and y is x - 3. The compound is useful as an adhesion promoter in a composition suitable as an encapsulant for a variety of applications including automotive, electrical, electronic and medical applications.

Description

[0001] Anhydride Functionalized Cyclic Polyorganosiloxane

[0002] Background of the Invention

[0003] The present invention relates to a compound which is an anhydride functionalized cyclic polyorganosiloxane. The compound of the present invention is useful as an adhesion promoter in a composition suitable as an encapsulant for a variety of applications including automotive, electrical, electronic and medical applications.

[0004] The adhesion of silicone-based compositions to substrates such as glass, metal, and a variety of plastics is facilitated with an adhesion promoter, which includes functionalized organosiloxanes.

[0005] For example, US 6,887,932 B2 (Azechi) discloses a vast number of adhesion promoters that are functionalized polyorganosiloxanes containing Si-H groups. CN 103467965 A (Shinetsu) discloses adhesion promoters that are cyclic organosiloxanes containing Si-H, anhydride, and fluoroalkyl groups. Similarly, EP 3 850 049 Bl (Felder) discloses adhesion promoters that are acid anhydride functionalized polyorganosiloxanes containing Si-H groups.

[0006] WO 2021 / 262830 (Santos) discloses a telechelic anhydride terminated polyorganosiloxane of the following formula: where n is from 2 to 20.

[0007] There is still a need to develop alternative solutions for adhesion promoters.

[0008] Summary of the Invention

[0009] The present invention addresses a need in the art by providing a compound of Formula 1 :

[0010] Formula 1 where each R is a Cs-Cn-alkyl anhydride group; the sum of m and n is in the range of from 1 to 4; and -DHX- is a mono- or diradical of the compound of Formula 2:

[0011] Formula 2 where x is from 3 to 10, and y is x - 3.

[0012] The compound of the present invention is useful as an adhesion promoter for polyorganosiloxane compositions. Detailed Description of the Invention

[0013] The present invention addresses a need in the art by providing a compound of Formula 1:

[0014] Formula 1 where each R is a C3-Ci2-alkyl anhydride group; the sum of m and n is in the range of from

[0015] 1 to 4; and -DHX- is a mono- or diradical of the compound of Formula 2:

[0016]

[0017] Formula 2 where x is from 3 to 10, and y is x - 3. In another embodiment, x is from 4 to 6.

[0018] Examples of suitable anhydride substituents include succinic anhydride, maleic anhydride, oxalic anhydride, and phthalic anhydride groups. Where the anhydride group is a succinic anhydride group, R is represented by the following fragment: where z is from 1 to 10, and where the dotted line represents the point of attachment to the DHXdiyl group.

[0019] DHXis represented by the compound of Formula 2. When x is 4, y is 1 . Thus, DH4 is represented by the compound of Formula 2a:

[0020] Formula 2a

[0021] In one embodiment, R1is phenyl, m is 1, n is 1, y is 1, and z is 1. Accordingly, a possible configuration of a compound of the present invention is represented by Formula 3:

[0022] Formula 3

[0023] It is understood that the R groups can be attached to any of the Si atoms of the DHXgroups and that the DHXgroups may be a blend of DHXgroups. For example, DHXmay be a mixture of DH4, DH5, and DH6. It is further understood that the compound of Formula 1 may comprise a blend of mono-, di-, tri-, and tetrasubstituted alkyl anhydride groups. In one embodiment, the compound of Formula 1 comprises a blend of mono- and disubstituted alkyl anhydride groups; i.e., m + n is in the range of 1 to 2.

[0024] The compound of Formula 1 (where m is 1 and n is 1) can be prepared in 2-steps, as illustrated: where Formula lois represented by the following formula:

[0025] Formula l0and Anh is an anhydride group. An example of a suitable acid catalyst is tris(pentafluorophenyl)borane (BCF).

[0026] The compound of the present invention has been found to be suitable as an adhesion promoter in a composition used to improve the adhesion of an organopolysiloxane to a substrate such as paper, metal, plastic, or glass.

[0027] Examples

[0028] Intermediate Example 1 - Preparation of Formula l0

[0029] A compound of Formula 2 (99.97 g, y is predominantly 1) then anhydrous toluene (49.97 g) were added to a N2 purged 1-L 3-neck round bottom flask equipped with a thermocouple, an overhead stirrer, and a septum. The contents of the flask were stirred, then BCF catalyst solution (0.32 g, 1% wt.% in toluene) was added. Diphenyldisilanol (56.07 g) was added in 4 portions over the course of ~1.5 h while maintaining a reaction temperature < 30 °C. The contents were stirred for an additional 1.5 h after addition was complete. A clear solution was obtained and treated with 36 pL of phenyl acetylene before volatiles were removed in vacuo at 80 °C.

[0030] Example - Preparation of a Compound of Formula 3

[0031] The compound of Formula lo(81.0 g) was charged into a three-neck round bottom flask and heated to 75 °C under N2 with stirring. Karstedt’s catalyst (5 ppm) was added, followed by the gradual addition of an allyl succinic anhydride solution (29.0 g in 7 g toluene). The addition rate was controlled so that the reaction mixture temperature did not exceed 80 °C. After completion of the addition, the reaction mixture was stirred at 75 °C under N2 for additional 1 h being allowed to cool to room temperature. 1-Ethynyl-l -cyclohexanol (0.43 g) was added to the mixture, after which time volatiles were removed in vacuo. Preparation of Liquid Silicone Rubber Formulations

[0032] Comparative Example - Preparation of a Liquid Silicone Rubber Formulation without Adhesion Promoter

[0033] A liquid silicone rubber (LSR) formulation was prepared by first forming two master batches generally in accordance with the procedure described in US 5,679,727, column 6. A first master batch (MB1) was prepared by combining fumed silica (surface area 300 m2 / g, 22.4 pbw) with a vinyl-terminated poly dimethylsiloxane (viscosity7= 53,000 mPa s at 25°C, 70.8 pbw), and contacting the blend with hexamethyldisilazane and water. A second master batch (MB2) was prepared by combining the fumed silica (24.8 pbw) with the vinyl-terminated polydimethylsiloxane (68.0 pbw), and contacting this blend with hexamethyldisilazane and l,l,3,3-tetramethyl-l,3-divinyldisilazane and water to give a vinyl functionalization of 0.08 mmol / g.

[0034] A portion of MB1 (17.7 pbw) was blended with a portion of MB2 (70.32 pbw) along with additional vinyl-terminated polydimethylsiloxane (6.52 pbw). Then, a vinyl-terminated polydimethylsiloxane-co-methylvinylsiloxane (1.16% vinyl functionality, viscosity = 370 mPa s at 25 °C, 5.06 pbw) was blended into the mixture along with Karstedt’s catalyst (0.0025 pbw), trimethyl-terminated polymethylhydrogen dimethylsiloxane (viscosity = 30 mPa s at 25 °C, 0.80 pbw), and ethinyl-cyclohexanol (0.04 pbw). The LSR was used shortly after preparation to prevent premature curing.

[0035] Example - Preparation of a Liquid Silicone Rubber Formulation with Adhesion Promoter

[0036] The example (LSR) formulation can be prepared as described above except for the following changes. The compound of Formula 3 (1.65 pbw) was added to the formulation at the last step, the amount of trimethyl-terminated polymethylhydrogen dimethylsiloxane was reduced to 0.39 pbw, and the amount of the additional vinyl-terminated polydimethylsiloxane was reduced to 5.29 pbw.

[0037] Peel Strength Testing Procedure

[0038] Two thermoplastic Ultradur B 4300 G4 Polybutylene Terephthalate 25 -mm x 100-mm substrates with a thickness of 3 mm were cleaned with isopropanol and dried for 18 h at 120 °C. The thermoplastic substrates were preheated at 150 °C for 5 min prior to overmolding with the LSR. Substrates were overmolded with a 3-mm layer of the LSR formulation, and compression molded for 5 min at 150 °C at a pressure of 300 bar.

[0039] Adhesion was tested in a 90° peel test using a floating roller device as described in DIN EN ISO 22631 (“Adhesives - Test method for adhesives for floor and wall coverings”). A tensile tester was used at a pulling speed of 100 mm / min. The peel strength was calculated as the average peel force, divided by the sample width (25 mm), and reported in N / mm. The adhesion test specimen containing the LSR that did not contain any adhesion promoter exhibited a peel strength of 0 N / mm, while the LSR containing the compound of Formula 3 exhibited a peel strength of 2.28 N / mm.

Claims

Claims:

1. A compound of Formula 1 :Formula 1 where each R is a Cs-Cn-alkyl anhydride group; the sum of m and n is in the range of from 1 to 4; and -DHX- is a mono- or diradical of the compound of Formula 2:Formula 2 where x is from 3 to 10; and y is x - 3.

2. The compound of Claim 1 wherein x is in the range of from 4 to 6; and m + n is in the range of from 1 to 2.

3. The compound of Claim 2 where x is 4.

4. The compound of Claim 1 which is represented by the following Formula 3:

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